Method For Purifying Reclaimed Polypropylene

ABSTRACT

A method for purifying a reclaimed polyethylene is provided. The method involves obtaining reclaimed polyethylene, contacting it with a first fluid solvent to produce an extracted reclaimed polyethylene then dissolving the extracted reclaimed polyethylene in a solvent to produce a first solution comprising polyethylene and suspended contaminants. The first solution is settled to produce a second solution comprising polyethylene and remaining contaminants. The second solution is purified by contacting the second solution with solid media to produce a third solution comprising purer polyethylene. Finally, the purer polyethylene is separated from the third solution.

FIELD OF THE INVENTION

The present invention generally relates to a method for purifyingcontaminated polymers through the use of a pressurized solvent and solidmedia. More specifically, this invention relates to a method forpurifying recycled polymers, such as post-consumer and post-industrialrecycled plastics, to produce a colorless or clear, odor free,virgin-like polymer. It is particularly useful for the purification ofpolyethylene.

BACKGROUND OF THE INVENTION

Polymers, especially synthetic plastics, are ubiquitous in daily lifedue to their relatively low production costs and good balance ofmaterial properties. Synthetic plastics are used in a wide variety ofapplications, such as packaging, automotive components, medical devices,and consumer goods. To meet the high demand of these applications, tensof billions of pounds of synthetic plastics are produced globally on anannual basis. The overwhelming majority of synthetic plastics areproduced from increasingly scarce fossil sources, such as petroleum andnatural gas. Additionally, the manufacturing of synthetic plastics fromfossil sources produces CO₂ as a by-product.

The ubiquitous use of synthetic plastics has consequently resulted inmillions of tons of plastic waste being generated every year. While themajority of plastic waste is landfilled via municipal solid wasteprograms, a significant portion of plastic waste is found in theenvironment as litter, which is unsightly and potentially harmful toecosystems. Plastic waste is often washed into river systems andultimately out to sea.

Plastics recycling has emerged as one solution to mitigate the issuesassociated with the wide-spread usage of plastics. Recovering andre-using plastics diverts waste from landfills and reduces the demandfor virgin plastics made from fossil-based resources, which consequentlyreduces greenhouse gas emissions. In developed regions, such as theUnited States and the European Union, rates of plastics recycling areincreasing due to greater awareness by consumers, businesses, andindustrial manufacturing operations. The majority of recycled materials,including plastics, are mixed into a single stream which is collectedand processed by a material recovery facility (MRF). At the MRF,materials are sorted, washed, and packaged for resale. Plastics can besorted into individual materials, such as high-density polyethylene(HDPE) or poly(ethylene terephthalate) (PET), or mixed streams of othercommon plastics, such as polypropylene (PP), low-density polyethylene(LDPE), poly(vinyl chloride) (PVC), polystyrene (PS), polycarbonate(PC), and polyamides (PA). The single or mixed streams can then befurther sorted, washed, and reprocessed into a pellet that is suitablefor re-use in plastics processing, for example blow and injectionmolding.

Though recycled plastics are sorted into predominately uniform streamsand are washed with aqueous and/or caustic solutions, the finalreprocessed pellet often remains highly contaminated with unwanted wasteimpurities, such as spoiled food residue and residual perfumecomponents. In addition, recycled plastic pellets, except for those fromrecycled beverage containers, are darkly colored due to the mixture ofdyes and pigments commonly used to colorize plastic articles. Whilethere are some applications that are insensitive to color andcontamination (for example black plastic paint containers and concealedautomotive components), the majority of applications require non-coloredpellets. The need for high quality, “virgin-like” recycled resin isespecially important for food and drug contact applications, such asfood packaging. In addition to being contaminated with impurities andmixed colorants, many recycled resin products are often heterogeneous inchemical composition and may contain a significant amount of polymericcontamination, such as recycled polypropylene contamination inpolyethylene and vice versa.

Mechanical recycling, also known as secondary recycling, is the processof converting recycled plastic waste into a re-usable form forsubsequent manufacturing. A more detailed review of mechanical recyclingand other plastics recovery processes are described in S. M. Al-Salem,P. Lettieri, J. Baeyens, “Recycling and recovery routes of plastic solidwaste (PSW): A review”, Waste Management, Volume 29, Issue 10, October2009, Pages 2625-2643, ISSN 0956-053X. While advances in mechanicalrecycling technology have improved the quality of recycled polymers tosome degree, there are fundamental limitations of mechanicaldecontamination approaches, such as the physical entrapment of pigmentswithin a polymer matrix. Thus, even with the improvements in mechanicalrecycling technology, the dark color and high levels of chemicalcontamination in currently available recycled plastic waste preventsbroader usage of recycled resins by the plastics industry.

To overcome the fundamental limitations of mechanical recycling, therehave been many methods developed to purify contaminated polymers viachemical approaches, or chemical recycling. Most of these methods usesolvents to decontaminate and purify polymers. The use of solventsenables the extraction of impurities and the dissolution of polymers,which further enables alternative separation technologies.

For example, U.S. Pat. No. 7,935,736 describes a method for recyclingpolyester from polyester-containing waste using a solvent to dissolvethe polyester prior to cleaning. The '736 patent also describes the needto use a precipitant to recover the polyester from the solvent.

In another example, U.S. Pat. No. 6,555,588 describes a method toproduce a polypropylene blend from a plastic mixture comprised of otherpolymers. The '588 patent describes the extraction of contaminants froma polymer at a temperature below the dissolution temperature of thepolymer in the selected solvent, such as hexane, for a specifiedresidence period. The '588 patent further describes increasing thetemperature of the solvent (or a second solvent) to dissolve the polymerprior to filtration. The '588 patent yet further describes the use ofshearing or flow to precipitate polypropylene from solution. Thepolypropylene blend described in the '588 patent contained polyethylenecontamination up to 5.6 wt %.

In another example, European Patent Application No. 849,312 (translatedfrom German to English) describes a process to obtain purifiedpolyolefins from a polyolefin-containing plastic mixture or apolyolefin-containing waste. The '312 patent application describes theextraction of polyolefin mixtures or wastes with a hydrocarbon fractionof gasoline or diesel fuel with a boiling point above 90° C. attemperatures between 90° C. and the boiling point of the hydrocarbonsolvent. The '312 patent application further describes contacting a hotpolyolefin solution with bleaching clay and/or activated carbon toremove foreign components from the solution. The '312 patent yet furtherdescribes cooling the solution to temperatures below 70° C. tocrystallize the polyolefin and then removing adhering solvent by heatingthe polyolefin above the melting point of the polyolefin, or evaporatingthe adhering solvent in a vacuum or passing a gas stream through thepolyolefin precipitate, and/or extraction of the solvent with an alcoholor ketone that boils below the melting point of the polyolefin.

In another example, U.S. Pat. No. 5,198,471 describes a method forseparating polymers from a physically commingled solid mixture (forexample waste plastics) containing a plurality of polymers using asolvent at a first lower temperature to form a first single phasesolution and a remaining solid component. The '471 patent furtherdescribes heating the solvent to higher temperatures to dissolveadditional polymers that were not solubilized at the first lowertemperature. The '471 patent describes filtration of insoluble polymercomponents.

In another example, U.S. Pat. No. 5,233,021 describes a method ofextracting pure polymeric components from a multi-component structure(for example waste carpeting) by dissolving each component at anappropriate temperature and pressure in a supercritical fluid and thenvarying the temperature and/or pressure to extract particular componentsin sequence. However, similar to the '471 patent, the '021 patent onlydescribes filtration of undissolved components.

In another example, U.S. Pat. No. 5,739,270 describes a method andapparatus for continuously separating a polymer component of a plasticfrom contaminants and other components of the plastic using a co-solventand a working fluid. The co-solvent at least partially dissolves thepolymer and the second fluid (that is in a liquid, critical, orsupercritical state) solubilizes components from the polymer andprecipitates some of the dissolved polymer from the co-solvent. The '270patent further describes the step of filtering thethermoplastic-co-solvent (with or without the working fluid) to removeparticulate contaminants, such as glass particles.

The known solvent-based methods to purify contaminated polymers, asdescribed above, do not produce “virgin-like” polymer. In the previousmethods, co-dissolution and thus cross contamination of other polymersoften occurs. If adsorbent is used, a filtration and/or centrifugationstep is often employed to remove the used adsorbent from solution. Inaddition, isolation processes to remove solvent, such as heating, vacuumevaporation, and/or precipitation using a precipitating chemical areused to produce a polymer free of residual solvent.

Accordingly, a need still exists for an improved solvent-based method topurify contaminated polymers that uses a solvent that is readily andeconomically removed from the polymer, is relatively simple in terms ofthe number of unit operations, produces a polymer without a significantamount of polymeric cross contamination, produces a polymer that isessentially colorless, and produces a polymer that is essentiallyodorless.

SUMMARY OF THE INVENTION

A method for purifying a reclaimed polyethylene is provided. The methodinvolves:

-   -   a. Obtaining reclaimed polyethylene selected from the group        consisting of post-consumer use polymers, post-industrial use        polymers, and combinations thereof;    -   b. Contacting the reclaimed polyethylene at a temperature from        about 80° C. to about 220° C. and at a pressure from about 150        psig (1.03 MPa) to about 15,000 psig (103.42 MPa) with a first        fluid solvent having a standard boiling point less than about        70° C., to produce an extracted reclaimed polyethylene;    -   c. Dissolving the extracted reclaimed polyethylene in a solvent        selected from the group consisting of the first fluid solvent, a        second fluid solvent, and mixtures thereof, at a temperature        from about 90° C. to about 220° C. and a pressure from about 350        psig (2.41 MPa) to about 20,000 psig (137.90 MPa) to produce a        first solution comprising polyethylene and suspended        contaminants;    -   d. Settling the first solution comprising polyethylene and        suspended contaminants at a temperature from about 90° C. to        about 220° C. and at a pressure from about 350 psig (2.41 MPa)        to about 20,000 psig (137.90 MPa) to produce a second solution        comprising polyethylene and remaining contaminants;    -   e. Purifying the second solution at a temperature from about        90° C. to about 220° C. and at a pressure from about 350 psig        (2.41 MPa) to about 20,000 psig (137.90 MPa) by contacting the        second solution with solid media to produce a third solution        comprising purer polyethylene; and    -   f. Separating the purer polyethylene from the third solution.        The second fluid solvent may have either the same chemical        composition or a different chemical composition than the first        fluid solvent.

In one embodiment, the polyethylene is separated from the third solutionat a temperature from about 0° C. to about 220° C. and a pressure fromabout 0 psig (0 MPa) to 2,000 psig (13.79 MPa). In another embodiment,the reclaimed polyethylene is dissolved in the fluid solvent, or fluidsolvent mixture, at a mass percent concentration of at least 0.5%. Inyet another embodiment, the reclaimed polyethylene is dissolved in thefluid solvent, or fluid solvent mixture, at a mass percent concentrationof at least 1%. In one embodiment, the reclaimed polyethylene isdissolved in the fluid solvent, or fluid solvent mixture, at a masspercent concentration of at least 2%.

In one embodiment, the reclaimed polyethylene is dissolved in the fluidsolvent, or fluid solvent mixture, at a mass percent concentration of atleast 3%. In another embodiment, the reclaimed polyethylene is dissolvedin the fluid solvent, or fluid solvent mixture, at a mass percentconcentration of at least 4%. In yet another embodiment, the reclaimedpolyethylene is dissolved in the fluid solvent, or fluid solventmixture, at a mass percent concentration of at least 5%.

In one embodiment, the reclaimed polyethylene is dissolved in the fluidsolvent, or fluid solvent mixture, at a mass percent concentration up to20%. In another embodiment, the reclaimed polyethylene is dissolved inthe fluid solvent, or fluid solvent mixture, at a mass percentconcentration up to 18%. In yet another embodiment, the reclaimedpolyethylene is dissolved in the fluid solvent, or fluid solventmixture, at a mass percent concentration up to 16%. In one embodiment,the reclaimed polyethylene is dissolved in the fluid solvent, or fluidsolvent mixture, at a mass percent concentration up to 14%. In anotherembodiment, the reclaimed polyethylene is dissolved in the fluidsolvent, or fluid solvent mixture, at a mass percent concentration up to12%.

In one embodiment, the reclaimed polyethylene is post-consumer recyclederived polyethylene. In another embodiment, the reclaimed polyethyleneis a polyethylene homopolymer or a primarily polyethylene copolymer. Inyet another embodiment, the fluid solvent has a standard boiling pointless than about 0° C. and greater than about −45° C. and a standardenthalpy change of vaporization of less than about +25 kJ/mol.

In one embodiment, the fluid solvent is selected from the groupconsisting of olefinic hydrocarbons, aliphatic hydrocarbons, andmixtures thereof. In another embodiment, the aliphatic hydrocarbon isselected from the group consisting of C₁-C₆ aliphatic hydrocarbons andmixtures thereof. In yet another embodiment, the aliphatic hydrocarbonsand mixtures thereof is comprised of primarily C₄ aliphatichydrocarbons.

In another embodiment, the fluid solvent consists essentially of C₄liquefied petroleum gas. In one embodiment, the fluid solvent isn-butane, butane isomers, or mixtures thereof. In another embodiment,the temperature in the contacting, dissolving, settling and purificationsteps is from about 110° C. to about 170° C.

In one embodiment, the pressure in the contacting step is from about1,100 psig (7.58 MPa) to about 5,500 psig (37.92 MPa). In anotherembodiment, the pressure in the contacting step is less than about 1,100psig (7.58 MPa). In yet another embodiment, the pressure in thedissolving, settling, and purification steps is greater than about 4,500psig (31.03 MPa). In one embodiment, the pressure in the dissolving,settling, and purification steps is greater than about 5,500 psig (37.92MPa).

In one embodiment, the solid media is selected from the group consistingof inorganic substances, carbon-based substances, and mixtures thereof.In another embodiment, the inorganic substances are selected from thegroup consisting of oxides of silicon, oxides of aluminum, oxides ofiron, aluminum silicates, amorphous volcanic glasses, and mixturesthereof. In yet another embodiment, the inorganic substances areselected from the group consisting of silica gel, diatomite, sand,quartz, alumina, perlite, fuller's earth, bentonite, and mixturesthereof.

In one embodiment, the carbon-based substances are selected from thegroup consisting of anthracite coal, carbon black, coke, activatedcarbon, cellulose, and mixtures thereof. In another embodiment, thecontacting of the polyethylene solution with said solid media is done ina packed bed of said solid media. In yet another embodiment, the packedbed is greater than 20 cm in length.

Additional features of the invention may become apparent to thoseskilled in the art from a review of the following detailed description,taken in conjunction with the examples.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block flow diagram showing the major steps of one embodimentof the present invention.

DETAILED DESCRIPTION OF THE INVENTION I. Definitions

As used herein, the term “reclaimed polymer” refers to a polymer usedfor a previous purpose and then recovered for further processing.

As used herein, the term “reclaimed polyethylene” refers to apolyethylene polymer used for a previous purpose and then recovered forfurther processing.

As used herein, the term “post-consumer” refers to a source of materialthat originates after the end consumer has used the material in aconsumer good or product.

As used herein, the term “post-consumer recycle” (PCR) refers to amaterial that is produced after the end consumer has used the materialand has disposed of the material in a waste stream.

As used herein, the term “post-industrial” refers to a source of amaterial that originates during the manufacture of a good or product.

As used herein, the term “fluid solvent” refers to a substance that mayexist in the liquid state under specified conditions of temperature andpressure. In some embodiments the fluid solvent may be a predominantlyhomogenous chemical composition of one molecule or isomer, while inother embodiments, the fluid solvent may be a mixture of severaldifferent molecular compositions or isomers. Further, in someembodiments of the present invention, the term “fluid solvent” may alsoapply to substances that are at, near, or above the critical temperatureand critical pressure (critical point) of that substance. It is wellknown to those having ordinary skill in the art that substances abovethe critical point of that substance are known as “supercritical fluids”which do not have the typical physical properties (i.e. density) of aliquid.

As used herein, the term “dissolved” means at least partialincorporation of a solute (polymeric or non-polymeric) in a solvent atthe molecular level. Further, the thermodynamic stability of thesolute/solvent solution can be described by the following equation 1:

ΔG _(mix) =ΔH _(m) −TΔS _(mix)  Equation 1

where ΔG_(mix) is the Gibbs free energy change of mixing of a solutewith a solvent, ΔH_(mix) is the enthalpy change of mixing, T is theabsolute temperature, and ΔS_(mix) is the entropy of mixing. To maintaina stable solution of a solute in a solvent, the Gibbs free energy mustbe negative and at a minimum. Thus, any combination of solute andsolvent that minimize a negative Gibbs free energy at appropriatetemperatures and pressures can be used for the present invention.

As used herein, the term “standard boiling point” refers to the boilingtemperature at an absolute pressure of exactly 100 kPa (1 bar, 14.5psia, 0.9869 atm) as established by the International Union of Pure andApplied Chemistry (IUPAC).

As used herein, the term “standard enthalpy change of vaporization”refers to the enthalpy change required to transform a specified quantityof a substance from a liquid into a vapor at the standard boiling pointof the substance.

As used herein, the term “polyethylene solution” refers to a solution ofpolyethylene dissolved in a solvent. The polyethylene solution maycontain undissolved matter and thus the polyethylene solution may alsobe a “slurry” of undissolved matter suspended in a solution ofpolyethylene dissolved in a solvent.

As used herein, the terms “sedimentation” and “settling” refer to thetendency of particles within a suspension to separate from a liquid inresponse to a force (typically a gravitational force) acting upon theparticles.

As used herein, the term “suspended contaminants” refers to unwanted orundesired constituents that are present throughout the bulk of medium ofa heterogeneous mixture.

As used herein, the term “solid media” refers to a substance that existsin the solid state under the conditions of use. The solid media may becrystalline, semi-crystalline, or amorphous. The solid media may begranular and may be supplied in different shapes (i.e. spheres,cylinders, pellets, etc.). If the solid media is granular, the particlesize and particle size distribution of solid media may be defined by themesh size used to classify the granular media. An example of standardmesh size designations can be found in the American Society for Testingand Material (ASTM) standard ASTM E11 “Standard Specification for WovenWire Test Sieve Cloth and Test Sieves.” The solid media may also be anon-woven fibrous mat or a woven textile.

As used herein, the term “purer polyethylene solution” refers to apolyethylene solution having fewer contaminants relative to the samepolyethylene solution prior to a purification step.

As used herein, the term “extraction” refers to the practice oftransferring a solute species from a liquid phase (or solid matrix)across a phase boundary to a separate immiscible liquid phase. Thedriving force(s) for extraction are described by partition theory.

As used herein, the term “extracted” refers to a material having fewersolute species relative to the same material prior to an extractionstep. As used herein, the term “extracted reclaimed polyethylene” refersto a reclaimed polyethylene having fewer solute species relative to thesame reclaimed polyethylene prior to an extraction step.

As used herein, the term “virgin-like” means essentiallycontaminant-free, pigment-free, odor-free, homogenous, and similar inproperties to virgin polymers.

As used herein, the term “primarily polyethylene copolymer” refers acopolymer with greater than 70 mol % of ethylene repeating units.

As used herein, any reference to international units of pressure (e.g.MPa) refers to gauge pressure.

II. Method for Purifying Contaminated Polyethylene

Surprisingly, it has been found that certain fluid solvents, which in apreferred embodiment exhibit temperature and pressure-dependentsolubility for polymers, when used in a relatively simple process can beused to purify contaminated polyethylene, especially reclaimed orrecycled polyethylene, to a near virgin-like quality. This process,exemplified in FIG. 1, comprises 1) obtaining a reclaimed polyethylene(step a in FIG. 1), followed by 2) extracting the polyethylene with afluid solvent at an extraction temperature (T_(E)) and at an extractionpressure (P_(E)) (step b in FIG. 1), followed by 3) dissolution of thepolyethylene in a fluid solvent at a dissolution temperature (T_(D)) andat a dissolution pressure (P_(D)) (step c in FIG. 1), followed by 4)sedimentation of the polymer solution at a dissolution temperature(T_(D)) and at a dissolution pressure (P_(D)) (step d in FIG. 1),followed by 5) contacting the dissolved polyethylene solution with solidmedia at a dissolution temperature (T_(D)) and at a dissolution pressure(P_(D)) (step e in FIG. 1), followed by separation of the polyethylenefrom the fluid solvent (step fin FIG. 1).

In one embodiment of the present invention, the purified polyethylene,which may be sourced from post-consumer waste streams, is essentiallycontaminant-free, pigment-free, odor-free, homogenous, and similar inproperties to virgin polymers. Furthermore, in a preferred embodiment,the physical properties of the fluid solvent of the present inventionmay enable more energy efficient methods for separation of the fluidsolvent from the purified polyethylene.

Reclaimed Polyethylene

In one embodiment of the present invention, a method for purifyingreclaimed polyethylene includes obtaining reclaimed polyethylene. Forthe purposes of the present invention, the reclaimed polyethylene issourced from post-consumer, post-industrial, post-commercial, and/orother special waste streams. For example, post-consumer wastepolyethylene can be derived from curbside recycle streams whereend-consumers place used polymers from packages and products into adesignated bin for collection by a waste hauler or recycler.Post-consumer waste polymers can also be derived from in-store“take-back” programs where the consumer brings waste polymers into astore and places the waste polymers in a designated collection bin. Anexample of post-industrial waste polymers can be waste polymers producedduring the manufacture or shipment of a good or product that arecollected as unusable material by the manufacturer (i.e. trim scraps,out of specification material, start up scrap). An example of wastepolymers from a special waste stream can be waste polymers derived fromthe recycling of electronic waste, also known as “e-waste.” Anotherexample of waste polymers from a special waste stream can be wastepolymers derived from the recycling of automobiles. Another example ofwaste polymers from a special waste stream can be waste polymers derivedfrom the recycling of used carpeting and textiles.

For the purposes of the present invention, the reclaimed polyethylene isa homogenous composition of an individual polymer or a mixture ofseveral different polyethylene compositions. Non-limiting examples ofpolyethylene compositions are homopolymers and copolymers of ethylene,such as high density polyethylene (HDPE), low density polyethylene(LDPE), linear low density polyethylene (LLDPE), copolymers of ethyleneand alpha-olefins, and other dissolvable polyethylene polymers that maybe apparent to those having ordinary skill in the art.

The reclaimed polyethylene may also contain various pigments, dyes,process aides, stabilizing additives, fillers, and other performanceadditives that were added to the polymer during polymerization orconversion of the original polymer to the final form of an article.Non-limiting examples of pigments are organic pigments, such as copperphthalocyanine, inorganic pigments, such as titanium dioxide, and otherpigments that may be apparent to those having ordinary skill in the art.A non-limiting example of an organic dye is Basic Yellow 51.Non-limiting examples of process aides are antistatic agents, such asglycerol monostearate and slip-promoting agents, such as erucamide. Anon-limiting example of a stabilizing additive isoctadecyl-3-(3,5-di-tert.butyl-4-hydroxyphenyl)-propionate. Non-limitingexamples of fillers are calcium carbonate, talc, and glass fibers.

Solvent

The fluid solvent of the present invention has a standard boiling pointless than about 70° C. Pressurization maintains solvents, which havestandard boiling points below the operating temperature range of thepresent invention, in a state in which there is little or no solventvapor. In one embodiment, the fluid solvent with a standard boilingpoint less than about 70° C. is selected from the group consisting ofcarbon dioxide, ketones, alcohols, ethers, esters, alkenes, alkanes, andmixtures thereof. Non-limiting examples of fluid solvents with standardboing points less than about 70° C. are carbon dioxide, acetone,methanol, dimethyl ether, diethyl ether, ethyl methyl ether,tetrahydrofuran, methyl acetate, ethylene, propylene, 1-butene,2-butene, isobutylene, 1-pentene, 2-pentene, branched isomers ofpentene, 1-hexene, 2-hexene, methane, ethane, propane, n-butane,isobutane, n-pentane, isopentane, neopentane, n-hexane, isomers ofisohexane, and other substances that may be apparent to those havingordinary skill in the art.

The selection of the fluid solvent used will dictate the temperature andpressure ranges used to perform the steps of the present invention. Areview of polymer phase behavior in solvents of the kind described bythe present invention is provided in the following reference: McHugh etal. (1999) Chem. Rev. 99:565-602.

Extraction

In one embodiment of the present invention, a method for purifyingpolyethylene includes contacting reclaimed polyethylene with a fluidsolvent at a temperature and at a pressure wherein the polymer isessentially insoluble in the fluid solvent. Although not wishing to bebound by any theory, applicants believe that the temperature andpressure-dependent solubility can be controlled in such a way to preventthe fluid solvent from fully solubilizing the polymer, however, thefluid solvent can diffuse into the polymer and extract any extractablecontamination. The extractable contamination may be residual processingaides added to the polymer, residual product formulations whichcontacted the polymer, such as perfumes and flavors, dyes, and any otherextractable material that may have been intentionally added orunintentionally became incorporated into the polymer, for example,during waste collection and subsequent accumulation with other wastematerials.

In one embodiment, the controlled extraction may be accomplished byfixing the temperature of the polymer/fluid solvent system and thencontrolling the pressure below a pressure, or pressure range, where thepolymer dissolves in the fluid solvent. In another embodiment, thecontrolled extraction is accomplished by fixing the pressure of thepolymer/solvent system and then controlling the temperature below atemperature, or temperature range where the polymer dissolves in thefluid solvent. The temperature and pressure-controlled extraction of thepolymer with a fluid solvent uses a suitable pressure vessel and may beconfigured in a way that allows for continuous extraction of the polymerwith the fluid solvent. In one embodiment of the present invention, thepressure vessel may be a continuous liquid-liquid extraction columnwhere molten polymer is pumped into one end of the extraction column andthe fluid solvent is pumped into the same or the opposite end of theextraction column. In another embodiment, the fluid containing extractedcontamination is removed from the process. In another embodiment, thefluid containing extracted contamination is purified, recovered, andrecycled for use in the extraction step or a different step in theprocess. In one embodiment of the present invention, the extraction maybe performed as a batch method, wherein the reclaimed polyethylene isfixed in a pressure vessel and the fluid solvent is continuously pumpedthrough the fixed polymer phase. The extraction time or the amount offluid solvent used will depend on the desired purity of the final purerpolymer and the amount of extractable contamination in the startingreclaimed polyethylene. In another embodiment, the fluid containingextracted contamination is contacted with solid media in a separate stepas described in the “Purification” section below. In another embodiment,a method for purifying reclaimed polyethylene includes contactingreclaimed polyethylene with a fluid solvent at a temperature and at apressure wherein the polymer is molten and in the liquid state. Inanother embodiment, the reclaimed polyethylene is contacted with thefluid solvent at a temperature and at a pressure wherein the polymer isin the solid state.

In one embodiment, a method for purifying reclaimed polyethyleneincludes contacting polyethylene with a fluid solvent at a temperatureand a pressure wherein the polyethylene remains essentially undissolved.In another embodiment, a method for purifying reclaimed polyethyleneincludes contacting polyethylene with n-butane at a temperature fromabout 80° C. to about 220° C. In another embodiment, a method forpurifying reclaimed polyethylene includes contacting polyethylene withn-butane at a temperature from about 100° C. to about 200° C. In anotherembodiment, a method for purifying reclaimed polyethylene includescontacting polyethylene with n-butane at a temperature from about 130°C. to about 180° C. In another embodiment, a method for purifyingreclaimed polyethylene includes contacting polyethylene with n-butane ata pressure from about 150 psig (1.03 MPa) to about 6,500 psig (44.82MPa). In another embodiment, a method for purifying reclaimedpolyethylene includes contacting polyethylene with n-butane at apressure from about 3,000 psig (20.68 MPa) to about 6,000 psig (41.37MPa). In another embodiment, a method for purifying reclaimedpolyethylene includes contacting polyethylene with n-butane at apressure from about 4,500 psig (31.03 MPa) to about 5,500 psig (37.92MPa).

In another embodiment, a method for purifying reclaimed polyethyleneincludes contacting polyethylene with propane at a temperature fromabout 80° C. to about 220° C. In another embodiment, a method forpurifying reclaimed polyethylene includes contacting polyethylene withpropane at a temperature from about 100° C. to about 200° C. In anotherembodiment, a method for purifying reclaimed polyethylene includescontacting polyethylene with propane at a temperature from about 130° C.to about 180° C. In another embodiment, a method for purifying reclaimedpolyethylene includes contacting polyethylene with propane at a pressurefrom about 1,000 psig (6.89 MPa) to about 15,000 psig (103.42 MPa). Inanother embodiment, a method for purifying reclaimed polyethyleneincludes contacting polyethylene with propane at a pressure from about2,000 psig (13.79 MPa) to about 10,000 psig (68.95 MPa). In anotherembodiment, a method for purifying reclaimed polyethylene includescontacting polyethylene with propane at a pressure from about 5,000 psig(34.47 MPa) to about 9,000 psig (62.05 MPa).

Dissolution

In one embodiment of the present invention, a method for purifyingreclaimed polyethylene includes dissolving the reclaimed polyethylene ina fluid solvent at a temperature and at a pressure wherein the polymeris dissolved in the fluid solvent. Although not wishing to be bound byany theory, applicants believe that the temperature and pressure can becontrolled in such a way to enable thermodynamically favorabledissolution of the reclaimed polymer in a fluid solvent. Furthermore,the temperature and pressure can be controlled in such a way to enabledissolution of a particular polymer or polymer mixture while notdissolving other polymers or polymer mixtures. This controllabledissolution enables the separation of polymers from polymer mixtures.

In one embodiment of the present invention, a method for purifyingpolymers includes dissolving contaminated reclaimed polyethylene in asolvent that does not dissolve the contaminants under the sameconditions of temperature and pressure. The contaminants may includepigments, fillers, dirt, and other polymers. These contaminants arereleased from the reclaimed polyethylene upon dissolution and thenremoved from the polymer solution via a subsequent solid-liquidseparation step.

In one embodiment of the present invention, a method for purifyingreclaimed polyethylene includes dissolving polyethylene in a fluidsolvent at a temperature and at a pressure wherein the polyethylene isdissolved in the fluid solvent. In another embodiment, a method forpurifying reclaimed polyethylene includes dissolving polyethylene inn-butane at a temperature from about 90° C. to about 220° C. In anotherembodiment, a method for purifying reclaimed polyethylene includesdissolving polyethylene in n-butane at a temperature from about 100° C.to about 200° C. In another embodiment, a method for purifying reclaimedpolyethylene includes dissolving polyethylene in n-butane at atemperature from about 130° C. to about 180° C. In another embodiment, amethod for purifying reclaimed polyethylene includes dissolvingpolyethylene in n-butane at a pressure from about 1,000 psig (6.89 MPa)to about 12,000 psig (82.74 MPa). In another embodiment, a method forpurifying reclaimed polyethylene includes dissolving polyethylene inn-butane at a pressure from about 2,000 psig (13.79 MPa) to about 10,000psig (68.95 MPa). In another embodiment, a method for purifyingreclaimed polyethylene includes dissolving polyethylene in n-butane at apressure from about 4,000 psig (27.58 MPa) to about 6,000 psig (41.37MPa). In another embodiment, a method for purifying reclaimedpolyethylene includes dissolving polyethylene in n-butane at a masspercent concentration of at least 0.5%. In another embodiment, thepolyethylene is dissolved at a mass percent concentration of at least1%. In another embodiment, the polyethylene is dissolved at a masspercent concentration of at least 2%. In another embodiment, thepolyethylene is dissolved at a mass percent concentration of at least3%. In another embodiment, the polyethylene is dissolved at a masspercent concentration of at least 4%. In another embodiment, thepolyethylene is dissolved at a mass percent concentration of at least5%. In another embodiment, a method for purifying reclaimed polyethyleneincludes dissolving polyethylene in n-butane at a mass percentconcentration up to 20%. In another embodiment, the polyethylene isdissolved at a mass percent concentration up to 18%. In anotherembodiment, the polyethylene is dissolved at a mass percentconcentration up to 16%. In another embodiment, the polyethylene isdissolved at a mass percent concentration up to 14%. In anotherembodiment, the polyethylene is dissolved at a mass percentconcentration up to 12%.

In another embodiment, a method for purifying reclaimed polyethyleneincludes dissolving polyethylene in propane at a temperature from about90° C. to about 220° C. In another embodiment, a method for purifyingreclaimed polyethylene includes dissolving polyethylene in propane at atemperature from about 100° C. to about 200° C. In another embodiment, amethod for purifying reclaimed polyethylene includes dissolvingpolyethylene in propane at a temperature from about 130° C. to about180° C. In another embodiment, a method for purifying reclaimedpolyethylene includes dissolving polyethylene in propane at a pressurefrom about 3,000 psig (20.68 MPa) to about 20,000 psig (137.90 MPa). Inanother embodiment, a method for purifying reclaimed polyethyleneincludes dissolving polyethylene in propane at a pressure from about5,000 psig (34.47 MPa) to about 15,000 psig (103.42 MPa). In anotherembodiment, a method for purifying reclaimed polyethylene includesdissolving polyethylene in propane at a pressure from about 8,000 psig(55.16 MPa) to about 11,000 psig (75.84 MPa). In another embodiment, amethod for purifying reclaimed polyethylene includes dissolvingpolyethylene in propane at a mass percent concentration of at least0.5%. In another embodiment, the polyethylene is dissolved at a masspercent concentration of at least 1%. In another embodiment, thepolyethylene is dissolved at a mass percent concentration of at least2%. In another embodiment, the polyethylene is dissolved at a masspercent concentration of at least 3%. In another embodiment, thepolyethylene is dissolved at a mass percent concentration of at least4%. In another embodiment, the polyethylene is dissolved at a masspercent concentration of at least 5%. In another embodiment, a methodfor purifying reclaimed polyethylene includes dissolving polyethylene inpropane at a mass percent concentration up to 20%. In anotherembodiment, the polyethylene is dissolved at a mass percentconcentration up to 18%. In another embodiment, the polyethylene isdissolved at a mass percent concentration up to 16%. In anotherembodiment, the polyethylene is dissolved at a mass percentconcentration up to 14%. In another embodiment, the polyethylene isdissolved at a mass percent concentration up to 12%.

Sedimentation

In one embodiment of the present invention, a method for purifyingpolyethylene includes separating the undissolved contaminants from thepolyethylene solution via a sedimentation (also known as settling) stepat a temperature and at a pressure wherein the polymer remains dissolvedin the fluid solvent. In one embodiment, the settling step causes theundissolved contaminants to experience a force that uniformly moves theundissolved contaminants in the direction of the force. Typically theapplied settling force is gravity, but can also be a centrifugal,centripetal, or some other force. The amount of applied force andduration of settling time will depend upon several parameters,including, but not limited to: particle size of the contaminantparticles, contaminant particle densities, density of the fluid orsolution, and the viscosity of the fluid or solution. The followingequation (equation 2) is a relationship between the aforementionedparameters and the settling velocity, which is a measure of thecontaminant sedimentation rate:

$\begin{matrix}{v = \frac{2\left( {\rho_{p} - \rho_{f}} \right)g\; r^{2}}{9\eta}} & {{Equation}\mspace{14mu} 2}\end{matrix}$

where v is the settling velocity, μ_(p) is the density of thecontaminant particle, μ_(f) is the density of the fluid or solution, gis the acceleration due to the applied force (typically gravity), r isthe radius of the contaminant particle and η is the dynamic viscosity ofthe fluid or solution. Some of the key parameters that determine thesolution viscosity are: the chemical composition of the fluid solvent,the molecular weight of the polymer dissolved in the fluid solvent, theconcentration of dissolved polymer in the fluid solvent, the temperatureof the fluid solvent solution, and the pressure of the fluid solventsolution.

In one embodiment, a method for purifying reclaimed polyethyleneincludes settling contaminants from a polyethylene/fluid solventsolution at a temperature and at a pressure wherein the polyethyleneremains dissolved in the fluid solvent. In another embodiment, a methodfor purifying reclaimed polyethylene includes settling contaminants froma polyethylene/n-butane solution at a temperature from about 90° C. toabout 220° C. In another embodiment, a method for purifying reclaimedpolyethylene includes settling contaminants from a polyethylene/n-butanesolution at a temperature from about 100° C. to about 200° C. In anotherembodiment, a method for purifying reclaimed polyethylene includessettling contaminants from a polyethylene/n-butane solution at atemperature from about 130° C. to about 180° C. In another embodiment, amethod for purifying reclaimed polyethylene includes settlingcontaminants from a polyethylene/n-butane solution at a pressure fromabout 1,000 psig (6.89 MPa) to about 12,000 psig (82.74 MPa). In anotherembodiment, a method for purifying reclaimed polyethylene includessettling contaminants from a polyethylene/n-butane solution at apressure about 2,000 psig (13.79 MPa) to about 10,000 psig (68.95 MPa).In another embodiment, a method for purifying reclaimed polyethyleneincludes settling contaminants from a polyethylene/n-butane solution ata pressure from about 4,000 psig (27.58 MPa) to about 6,000 psig (41.37MPa). In another embodiment, a method for purifying reclaimedpolyethylene includes settling contaminants from a polyethylene/n-butanesolution wherein the polyethylene is dissolved at a mass percentconcentration of at least 0.5%. In another embodiment, the polyethyleneis dissolved at a mass percent concentration of at least 1%. In anotherembodiment, the polyethylene is dissolved at a mass percentconcentration of at least 2%. In another embodiment, the polyethylene isdissolved at a mass percent concentration of at least 3%. In anotherembodiment, the polyethylene is dissolved at a mass percentconcentration of at least 4%. In another embodiment, the polyethylene isdissolved at a mass percent concentration of at least 5%. In anotherembodiment, a method for purifying reclaimed polyethylene includessettling contaminants from a polyethylene/n-butane solution where in thepolyethylene is dissolved at a mass percent concentration up to 20%. Inanother embodiment, the polyethylene is dissolved at a mass percentconcentration up to 18%. In another embodiment, the polyethylene isdissolved at a mass percent concentration up to 16%. In anotherembodiment, the polyethylene is dissolved at a mass percentconcentration up to 14%. In another embodiment, the polyethylene isdissolved at a mass percent concentration up to 12%.

In another embodiment, a method for purifying reclaimed polyethyleneincludes settling contaminants from a polyethylene/propane solution at atemperature from about 90° C. to about 220° C. In another embodiment, amethod for purifying reclaimed polyethylene includes settlingcontaminants from a polyethylene/propane solution with at a temperaturefrom about 100° C. to about 200° C. In another embodiment, a method forpurifying reclaimed polyethylene includes settling contaminants from apolyethylene/propane solution at a temperature from about 130° C. toabout 180° C. In another embodiment, a method for purifying reclaimedpolyethylene includes settling contaminants from a polyethylene/propanesolution at a pressure from about 3,000 psig (20.68 MPa) to about 20,000psig (137.90 MPa). In another embodiment, a method for purifyingreclaimed polyethylene includes settling contaminants from apolyethylene/propane solution at a pressure from about 5,000 psig (34.47MPa) to about 15,000 psig (103.42 MPa). In another embodiment, a methodfor purifying reclaimed polyethylene includes settling contaminants froma polyethylene/propane solution with at a pressure from about 8,000 psig(55.16 MPa) to about 11,000 psig (75.84 MPa). In another embodiment, amethod for purifying reclaimed polyethylene includes settlingcontaminants from a polyethylene/propane solution wherein thepolyethylene is dissolved at a mass percent concentration of at least0.5%. In another embodiment, the polyethylene is dissolved at a masspercent concentration of at least 1%. In another embodiment, thepolyethylene is dissolved at a mass percent concentration of at least2%. In another embodiment, the polyethylene is dissolved at a masspercent concentration of at least 3%. In another embodiment, thepolyethylene is dissolved at a mass percent concentration of at least4%. In another embodiment, the polyethylene is dissolved at a masspercent concentration of at least 5%. In another embodiment, a methodfor purifying reclaimed polyethylene includes settling contaminants froma polyethylene/propane solution where in the polyethylene is dissolvedat a mass percent concentration up to 20%. In another embodiment, thepolyethylene is dissolved at a mass percent concentration up to 18%. Inanother embodiment, the polyethylene is dissolved at a mass percentconcentration up to 16%. In another embodiment, the polyethylene isdissolved at a mass percent concentration up to 14%. In anotherembodiment, the polyethylene is dissolved at a mass percentconcentration up to 12%.

Purification

In one embodiment of the present invention, a method for purifyingpolyethylene includes contacting a contaminated polymer solution withsolid media at a temperature and at a pressure wherein the polymerremains dissolved in the fluid solvent. The solid media of the presentinvention is any solid material that removes at least some of thecontamination from a solution of reclaimed polyethylene dissolved in thefluid solvent of the present invention. Although not wishing to be boundby any theory, the applicants believe that the solid media removescontamination by a variety of mechanisms. Non-limiting examples ofpossible mechanisms include adsorption, absorption, size exclusion, ionexclusion, ion exchange, and other mechanisms that may be apparent tothose having ordinary skill in the art. Furthermore, the pigments andother contaminants commonly found in reclaimed polyethylene may be polarcompounds and may preferentially interact with the solid media, whichmay also be at least slightly polar. The polar-polar interactions areespecially favorable when non-polar solvents, such as alkanes, are usedas the fluid solvent.

In one embodiment of the present invention, the solid media is selectedfrom the group consisting of inorganic substances, carbon-basedsubstances, or mixtures thereof. Useful examples of inorganic substancesinclude oxides of silicon, oxides of aluminum, oxides of iron, aluminumsilicates, magnesium silicates, amorphous volcanic glasses, silica,silica gel, diatomite, sand, quartz, reclaimed glass, alumina, perlite,fuller's earth, bentonite, and mixtures thereof. Useful examples ofcarbon-based substances include anthracite coal, carbon black, coke,activated carbon, cellulose, and mixtures thereof. In another embodimentof the present invention, the solid media is recycled glass.

In one embodiment of the present invention, the solid media is contactedwith the polymer in a vessel for a specified amount of time while thesolid media is agitated. In another embodiment, the solid media isremoved from the purer polymer solution via a solid-liquid separationstep. Non-limiting examples of solid-liquid separation steps includefiltration, decantation, centrifugation, and settling. In anotherembodiment of the present invention, the contaminated polymer solutionis passed through a stationary bed of solid media. In another embodimentof the present invention, the height or length of the stationary bed ofsolid media is greater than 5 cm. In another embodiment of the presentinvention, the height or length of the stationary bed of solid media isgreater than 10 cm. In another embodiment of the present invention, theheight or length of the stationary bed of solid media is greater than 20cm. In another embodiment of the present invention, the solid media isreplaced as needed to maintain a desired purity of polymer. In yetanother embodiment, the solid media is regenerated and re-used in thepurification step. In another embodiment, the solid media is regeneratedby fluidizing the solid media during a backwashing step.

In one embodiment, a method for purifying reclaimed polyethyleneincludes contacting a polyethylene/fluid solvent solution with solidmedia at a temperature and a pressure wherein the polyethylene remainsdissolved in the fluid solvent. In another embodiment, a method forpurifying reclaimed polyethylene includes contacting apolyethylene/n-butane solution with solid media at a temperature fromabout 90° C. to about 220° C. In another embodiment, a method forpurifying reclaimed polyethylene includes contacting apolyethylene/n-butane solution with solid media at a temperature fromabout 100° C. to about 200° C. In another embodiment, a method forpurifying reclaimed polyethylene includes contacting apolyethylene/n-butane solution with solid media at a temperature fromabout 130° C. to about 180° C. In another embodiment, a method forpurifying reclaimed polyethylene includes contacting apolyethylene/n-butane solution with solid media at a pressure from about1,000 psig (6.89 MPa) to about 12,000 psig (82.74 MPa). In anotherembodiment, a method for purifying reclaimed polyethylene includescontacting a polyethylene/n-butane solution with solid media at apressure from about 2,000 psig (13.79 MPa) to about 10,000 psig (68.95MPa). In another embodiment, a method for purifying reclaimedpolyethylene includes contacting a polyethylene/n-butane solution withsolid media at a pressure from about 4,000 psig (27.58 MPa) to about6,000 psig (41.37 MPa). In another embodiment, a method for purifyingreclaimed polyethylene includes contacting a polyethylene/n-butanesolution with solid media wherein the polyethylene is dissolved at amass percent concentration of at least 0.5%. In another embodiment, thepolyethylene is dissolved at a mass percent concentration of at least1%. In another embodiment, the polyethylene is dissolved at a masspercent concentration of at least 2%. In another embodiment, thepolyethylene is dissolved at a mass percent concentration of at least3%. In another embodiment, the polyethylene is dissolved at a masspercent concentration of at least 4%. In another embodiment, thepolyethylene is dissolved at a mass percent concentration of at least5%. In another embodiment, a method for purifying reclaimed polyethyleneincludes contacting a polyethylene/n-butane solution with solid mediawherein the polyethylene is dissolved at a mass percent concentration upto 20%. In another embodiment, the polyethylene is dissolved at a masspercent concentration up to 18%. In another embodiment, the polyethyleneis dissolved at a mass percent concentration up to 16%. In anotherembodiment, the polyethylene is dissolved at a mass percentconcentration up to 14%. In another embodiment, the polyethylene isdissolved at a mass percent concentration up to 12%.

In another embodiment, a method for purifying reclaimed polyethyleneincludes contacting a polyethylene/propane solution with solid media ata temperature from about 90° C. to about 220° C. In another embodiment,a method for purifying reclaimed polyethylene includes contacting apolyethylene/propane solution with solid media at a temperature fromabout 100° C. to about 200° C. In another embodiment, a method forpurifying reclaimed polyethylene includes contacting apolyethylene/propane solution with solid media at a temperature fromabout 130° C. to about 180° C. In another embodiment, a method forpurifying reclaimed polyethylene includes contacting apolyethylene/propane solution with solid media at a pressure from about3,000 psig (20.68 MPa) to about 20,000 psig (137.90 MPa). In anotherembodiment, a method for purifying reclaimed polyethylene includescontacting a polyethylene/propane solution with solid media at apressure from about 5,000 psig (34.47 MPa) to about 15,000 psig (103.42MPa). In another embodiment, a method for purifying reclaimedpolyethylene includes contacting a polyethylene/propane solution withsolid media at a pressure from about 8,000 psig (55.16 MPa) to about11,000 psig (75.84 MPa). In another embodiment, a method for purifyingreclaimed polyethylene includes contacting a polyethylene/propanesolution with solid media wherein the polyethylene is dissolved at amass percent concentration of at least 0.5%. In another embodiment, thepolyethylene is dissolved at a mass percent concentration of at least1%. In another embodiment, the polyethylene is dissolved at a masspercent concentration of at least 2%. In another embodiment, thepolyethylene is dissolved at a mass percent concentration of at least3%. In another embodiment, the polyethylene is dissolved at a masspercent concentration of at least 4%. In another embodiment, thepolyethylene is dissolved at a mass percent concentration of at least5%. In another embodiment, a method for purifying reclaimed polyethyleneincludes contacting a polyethylene/propane solution with solid mediawherein the polyethylene is dissolved at a mass percent concentration upto 20%. In another embodiment, the polyethylene is dissolved at a masspercent concentration up to 18%. In another embodiment, the polyethyleneis dissolved at a mass percent concentration up to 16%. In anotherembodiment, the polyethylene is dissolved at a mass percentconcentration up to 14%. In another embodiment, the polyethylene isdissolved at a mass percent concentration up to 12%.

Separation

In one embodiment of the present invention, a method for purifyingreclaimed polyethylene includes separating the purer polymer from thefluid solvent at a temperature and at a pressure wherein the polymerprecipitates from solution and is no longer dissolved in the fluidsolvent. In another embodiment, the precipitation of the purer polymerfrom the fluid solvent is accomplished by reducing the pressure at afixed temperature. In another embodiment, the precipitation of the purerpolymer from the fluid solvent is accomplished by reducing thetemperature at a fixed pressure. In another embodiment, theprecipitation of the purer polymer from the fluid solvent isaccomplished by increasing the temperature at a fixed pressure. Inanother embodiment, the precipitation of the purer polymer from thefluid solvent is accomplished by reducing both the temperature andpressure. The solvent can be partially or completely converted from theliquid to the vapor phase by controlling the temperature and pressure.In another embodiment, the precipitated polymer is separated from thefluid solvent without completely converting the fluid solvent into a100% vapor phase by controlling the temperature and pressure of thesolvent during the separation step. The separation of the precipitatedpurer polymer is accomplished by any method of liquid-liquid orliquid-solid separation. Non-limiting examples of liquid-liquid orliquid-solid separations include filtration, decantation,centrifugation, and settling.

In one embodiment, a method for purifying reclaimed polyethyleneincludes separating polyethylene from a polyethylene/fluid solventsolution at a temperature and a pressure wherein the polyethyleneprecipitates from solution. In another embodiment, a method forpurifying reclaimed polyethylene includes separating polyethylene from apolyethylene/n-butane solution at a temperature from about 0° C. toabout 220° C. In another embodiment, a method for purifying reclaimedpolyethylene includes separating polyethylene from apolyethylene/n-butane solution at a temperature from about 50° C. toabout 175° C. In another embodiment, a method for purifying reclaimedpolyethylene includes separating polyethylene from apolyethylene/n-butane solution at a temperature from about 100° C. toabout 160° C. In another embodiment, a method for purifying reclaimedpolyethylene includes separating polyethylene from apolyethylene/n-butane solution at a pressure from about 0 psig (0 MPa)to about 4,000 psig (27.58 MPa). In another embodiment, a method forpurifying reclaimed polyethylene includes separating polyethylene from apolyethylene/n-butane solution at a pressure from about 50 psig (0.34MPa) to about 2,000 psig (13.79 MPa). In another embodiment, a methodfor purifying reclaimed polyethylene includes separating polyethylenefrom a polyethylene/n-butane solution at a pressure from about 75 psig(0.52 MPa) to about 1,000 psig (6.89 MPa).

In another embodiment, a method for purifying reclaimed polyethyleneincludes separating polyethylene from a polyethylene/propane solution ata temperature from about −42° C. to about 220° C. In another embodiment,a method for purifying reclaimed polyethylene includes separatingpolyethylene from a polyethylene/propane solution at a temperature fromabout 0° C. to about 150° C. In another embodiment, a method forpurifying reclaimed polyethylene includes separating polyethylene from apolyethylene/propane solution at a temperature from about 50° C. toabout 130° C. In another embodiment, a method for purifying reclaimedpolyethylene includes separating polyethylene from apolyethylene/propane solution at a pressure from about 0 psig (0 MPa) toabout 15,000 psig (103.42 MPa). In another embodiment, a method forpurifying reclaimed polyethylene includes separating polyethylene from apolyethylene/propane solution at a pressure from about 50 psig (0.34MPa) to about 5,000 psig (34.48 MPa). In another embodiment, a methodfor purifying reclaimed polyethylene includes separating polyethylenefrom a polyethylene/propane solution at a pressure from about 75 psig(0.52 MPa) to about 1,000 psig (6.89 MPa).

Every document cited herein, including any cross reference or relatedpatent or patent application, is hereby incorporated herein by referencein its entirety unless expressly excluded or otherwise limited. Thecitation of any document is not an admission that it is prior art withrespect to any invention disclosed or claimed herein or that it alone,or in any combination with any other reference or references, teaches,suggest or discloses any such invention. Further, to the extent that anymeaning or definition of a term in this document conflicts with anymeaning or definition of the same term in a document incorporated byreference, the meaning or definition assigned to that term in thisdocument shall govern.

While particular embodiments of the present invention have beenillustrated and described, it would be obvious to those skilled in theart that various other changes and modification can be made withoutdeparting from the spirit and scope of the invention. It is thereforeintended to cover in the appended claims all such changes andmodification that are within the scope of the present invention.

What is claimed is:
 1. A method for purifying reclaimed polyethylenecomprising: a. Obtaining the reclaimed polyethylene wherein saidreclaimed polyethylene is selected from the group consisting ofpost-consumer use polymers, post-industrial use polymers, andcombinations thereof; b. Contacting the reclaimed polyethylene at atemperature from about 80° C. to about 220° C. and ata pressure fromabout 150 psig (1.03 MPa) to about 15,000 psig (103.42 MPa) with a firstfluid solvent having a standard boiling point less than about 70° C., toproduce an extracted reclaimed polyethylene; c. Dissolving the extractedreclaimed polyethylene in a solvent selected from the group consistingof the first fluid solvent, a second fluid solvent, and mixturesthereof, at a temperature from about 90° C. to about 220° C. and apressure from about 350 psig (2.41 MPa) to about 20,000 psig (137.90MPa) to produce a first solution comprising polyethylene and suspendedcontaminants; d. Settling said first solution comprising polyethyleneand suspended contaminants at a temperature from about 90° C. to about220° C. and at a pressure from about 350 psig (2.41 MPa) to about 20,000psig (137.90 MPa) to produce a second solution comprising polyethyleneand remaining contaminants; e. Purifying said second solution at atemperature from about 90° C. to about 220° C. and at a pressure fromabout 350 psig (2.41 MPa) to about 20,000 psig (137.90 MPa) bycontacting said second solution with solid media to produce a thirdsolution comprising purer polyethylene; and f. Separating said purerpolyethylene from said third solution; wherein said second fluid solventhas the same chemical composition or a different chemical composition asthe first fluid solvent.
 2. The method of claim 1, wherein saidpolyethylene is separated from said third solution at a temperature fromabout 0° C. to about 220° C. and a pressure from about 0 psig (0 MPa) to2,000 psig (13.79 MPa).
 3. The method of claim 1, wherein said reclaimedpolyethylene is dissolved in the fluid solvent, or fluid solventmixture, at a mass percent concentration of at least 0.5%.
 4. The methodof claim 1, wherein said reclaimed polyethylene is dissolved in thefluid solvent, or fluid solvent mixture, at a mass percent concentrationof at least 1%.
 5. The method of claim 1, wherein said reclaimedpolyethylene is dissolved in the fluid solvent, or fluid solventmixture, at a mass percent concentration of at least 2%.
 6. The methodof claim 1, wherein said reclaimed polyethylene is dissolved in thefluid solvent, or fluid solvent mixture, at a mass percent concentrationof at least 3%.
 7. The method of claim 1, wherein said reclaimedpolyethylene is dissolved in the fluid solvent, or fluid solventmixture, at a mass percent concentration of at least 4%.
 8. The methodof claim 1, wherein said reclaimed polyethylene is dissolved in thefluid solvent, or fluid solvent mixture, at a mass percent concentrationof at least 5%.
 9. The method of claim 1, wherein said reclaimedpolyethylene is dissolved in the fluid solvent, or fluid solventmixture, at a mass percent concentration up to 20%
 10. The method ofclaim 1, wherein said reclaimed polyethylene is dissolved in the fluidsolvent, or fluid solvent mixture, at a mass percent concentration up to18%
 11. The method of claim 1, wherein said reclaimed polyethylene isdissolved in the fluid solvent, or fluid solvent mixture, at a masspercent concentration up to 16%
 12. The method of claim 1, wherein saidreclaimed polyethylene is dissolved in the fluid solvent, or fluidsolvent mixture, at a mass percent concentration up to 14%
 13. Themethod of claim 1, wherein said reclaimed polyethylene is dissolved inthe fluid solvent, or fluid solvent mixture, at a mass percentconcentration up to 12%
 14. The method of claim 1, wherein the reclaimedpolyethylene is post-consumer recycle derived polyethylene.
 15. Themethod of claim 1, wherein said polyethylene is a polyethylenehomopolymer or a primarily polyethylene copolymer.
 16. The method ofclaim 1, wherein said fluid solvent has a standard boiling point lessthan about 0° C. and greater than about −45° C. and a standard enthalpychange of vaporization of less than about +25 kJ/mol.
 17. The method ofclaim 1, wherein said fluid solvent is selected from the groupconsisting of olefinic hydrocarbons, aliphatic hydrocarbons, andmixtures thereof.
 18. The method of claim 17, wherein said aliphatichydrocarbon is selected from the group consisting of C₁-C₆ aliphatichydrocarbons and mixtures thereof.
 19. The method of claim 17, whereinsaid aliphatic hydrocarbons and mixtures thereof is comprised ofprimarily C₄ aliphatic hydrocarbons.
 20. The method of claim 17, whereinsaid fluid solvent consists essentially of C₄ liquefied petroleum gas.21. The method of claim 17, wherein said fluid solvent is n-butane,butane isomers, or mixtures thereof.
 22. The method of claim 1, whereinsaid temperature in the contacting, dissolving, settling andpurification steps is from about 110° C. to about 170° C.
 23. The methodof claim 1, wherein said pressure in the contacting step is from about1,100 psig (7.58 MPa) to about 5,500 psig (37.92 MPa).
 24. The method ofclaim 1, wherein said pressure in the contacting is less than about1,100 psig (7.58 MPa).
 25. The method of claim 1, wherein said pressurein the dissolving, settling, and purification steps is greater thanabout 4,500 psig (31.03 MPa).
 26. The method of claim 1, wherein saidpressure in the dissolving, settling, and purification steps is greaterthan about 5,500 psig (37.92 MPa).
 27. The method of claim 1, whereinsaid solid media is selected from the group consisting of inorganicsubstances, carbon-based substances, and mixtures thereof.
 28. Themethod of claim 27, wherein said inorganic substances are selected fromthe group consisting of oxides of silicon, oxides of aluminum, oxides ofiron, aluminum silicates, amorphous volcanic glasses, and mixturesthereof.
 29. The method of claim 27, wherein said inorganic substancesare selected from the group consisting of silica gel, diatomite, sand,quartz, alumina, perlite, fuller's earth, bentonite, and mixturesthereof.
 30. The method of claim 27, wherein said carbon-basedsubstances are selected from the group consisting of anthracite coal,carbon black, coke, activated carbon, cellulose, and mixtures thereof.31. The method of claim 1, wherein said contacting of the polyethylenesolution with said solid media is done in a packed bed of said solidmedia.
 32. The method of claim 31, where said packed bed is greater than20 cm in length.